The present invention relates to an automatic diagnostic device for a separately driven, four-stroke-internal combustion engine with a flywheel mounted on the crankshaft, a camshaft driven by a pinion via the crankshaft and a ring gear on the flywheel for co-action with a starter pinion, comprising a measuring device for the detection and indication of a specific reference angular position of the crank drive, in particular of the ignition, top dead-center of a specific cylinder.